1. Field of the Invention
The present invention relates to a method of increasing the ductility of articles formed from superplastic alloy.
2. Prior Art
In our British Pat. No. 1,452,646, a process is described for the preparation of superplastic aluminium/calcium alloys. This patent disclosed aluminium alloys containing from 5 to 10% by weight of calcium, preferably 7.6% calcium, with a maximum of 1% by weight of impurities. These alloys are prepared by melting all their pure constituents together in the absence of oxygen, after which the alloy is subjected to mechanical treatment at a temperature of at least 270.degree. C. This mechanical treatment comprises rolling, pressing and working of this type.
The alloys thus obtained exhibit excellent properties of superplasticity and corrosion resistance. However, articles obtained by the superplastic deformation (using the conventional methods of experts in superplastic forming) of sheets, tubes etc. of these alloys have less ductility at the utilization temperature than the usual commercial alloys of aluminium.
It is an object of the present invention to provide articles formed from superplastic alloy having improved ductility.